I don't suppose David Cameron spends much time in Miss Sixty. If he were to inspect any teenage underwear counters, he might be surprised at the lack of 'harmful and creepy' offerings. Thongs have largely been replaced by 'boy shorts', a garment substantial enough to see an Angela Brazil heroine through a lacrosse tournament. Skirt hems sometimes almost graze the knee.

Mr Cameron's outburst against high street stores was very last season. The Bhs 'Little Miss Naughty' range of padded bras for under-10s, of which he complained in his speech on corporate responsibility, was withdrawn three years ago, and Next long since stopped selling T-shirts bearing the slogan: 'So many boys... so little time'. Asda and Argos have also ditched Lolita chic.

So, naturally, retailers reacted as if the Tory leader had complained about the prevalence of phossy jaw in pre-teen, match factory employees. Exposing Mr Cameron's mistake is unlikely, though, to harm him, when sexualising children is one of the great modern terrors. Kids Growing Older Younger, the syndrome he cites, evokes the image of a 21st-century Alice gazing into a looking glass and seeing a Joan Collins maquillage pout back.

But this isn't just about image. Here, as evidence of the death of childhood, is Britain's 'youngest' mother-to-be, who says she lost her virginity, at the age of 11, to a 15-year-old boy in a drunken one-night stand. The girl is looking forward to motherhood. She wants a son and plans to call him Leo, she tells the Sun during an interview in which she chainsmokes roll-ups.

She knows how to change nappies and give bottles, she says. But sick babies make her cry and she is frightened to bathe a slippery infant. The story is billed as 'a tragic sign of our times', as if this individual catastrophe is a parable for a degenerate country. Are we such terrible parents? Have we robbed our children of their youth? Leave sex aside, for a moment, and it is not difficult to find some answers.

Adults have been enthralled by precocity in childhood since the 12-year-old Jesus stunned the rabbis with his knowledge. Prodigies, from Picasso to Lisa Simpson, are held in awe. Pushy parents play Mozart to babies in the womb, in the hope of osmotically transmitting underage genius, or at least some whiff of advantage that will give their offspring a quick getaway in the race for the best life.

At worst, the fascination is abusive. Budhia Singh, a veteran Indian marathon star of four years old, was fêted as a national hero until last week, when the loneliness of the long-distance toddler belatedly became a story of child cruelty, in which a little boy was obliged to run until his fragile legs gave way. Budhia's fate is simply an extreme example of the trend towards premature adulthood. In America, where 26 per cent of under-twos have a television in their bedrooms, a new channel is offering all-day viewing for babies of six months upwards.

Despite the British obsession with juvenile obesity, BabyFirstTV will apparently be here by Christmas, offering visual Ritalin for cradle couch potatoes. Among older children, the charity, Kidscape, has just identified a breed of overindulged 'brat bullies'. This charge of poor parenting among the wealthy, echoed by a head teachers' leader claiming millions of children do badly at school because their guilt-ridden parents let them stay up too late, is not exactly surprising. It does, though, change the focus of the debate.

The middle classes, anguished about parenting, do not want to hear of their own defects. How much more comforting to dwell on the low-life failures whose children, bereft of dreams, betray their role as gatekeepers of purity. These Asbo Alices and their no-hope boyfriends have ravaged innocence and littered Eden with their Silk Cut stubs, used condoms and Smirnoff Ice bottles.

Family values must be resurrected, conservatives cry. Even Hillary Clinton is at it, reminding New York's Village Voice of 'the second coming of John Wesley' with her suggestion that teenage pregnancy might be cut by young people accepting 'religious and moral values'. Forget it. The cult of abstinence, despite some traction in America, failed to brainwash British children. That does not imply that all teenagers have sex too coldly or too young. It does mean that childhood, like Bhs's doomed knickers, is deemed a discontinued line.

There are several myths at work here. First, anyone romanticising traditional childhood should read some Dickens. For all the current fear about commercialisation, over-exposure to Claire's Accessories is hardly deadly. Adults should worry less about the material child and more about the poor one. Among other losers, some, such as young offenders, are treated brutally by a government prone to demonise the young. Some are neglected by chaotic parents or micro-managed by disappointed ones who want their children to be the over-achievers they never were. But this is by no means a bad time to be a child.

Second, the idealised nuclear family is a modern invention that peaked in the 1950s as a result of a baby boom and the spread of mass culture. For many centuries, war, short lives and deferred marriage ordained the complicated, sprawling family model to which we may be reverting today.

Third, the panic about bad children is always overdone. 'Yob culture' is just another branch of victimhood, and teenage pregnancy, though way too high, is finally declining. In Cambridgeshire, the last recorded figures show a drop of 18.6 per cent, against a national decrease of 11.1 per cent, after a drive to get teenagers to have safe sex. The fall coincided with a rise in GCSE grades, with the county's boys improving at three times the national level.

Traditionalists, though, prefer edict to persuasion. Even liberals fret that there is no longer a set etiquette on anything from how long a games console takes to fry the cortex to when a boyfriend should be allowed to stay the night. In the absence of such oracles as God and Dr Spock, adults rely on television gurus like Supernanny or study Brat Camp for proof that someone else's child is worse than theirs.

Government weighs in, with all the slipper-and-castor-oil remedies of the nanny state, and many fear that parents are failing to pass a framework of values on to their children. In some cases, that is true. But, equally, no one stresses the strengths of the 21st-century child who copes with her parents' divorces or their long absences at the office, and often grows stronger as a result.

We want our children to behave like adults - to be resilient, independent, industrious, stoic, even when separations break their hearts and when families expand or shrink, confounding all their certainties. We want them to be both old and young - to be our underlings and our equals, our babies and our friends. The slutty, pre-teen clothes that appalled David Cameron were bought by adults, not by children. Grow up, we tell them, if they misbehave. And then we are scandalised when they do.

But, for all the obituaries, childhood is not dead. It has merely been adapted, as in every century, to fit the circumstances of the time. In many ways, today's children have a better relationship with their parents than any other cohort in history. There is, though, a new tension, imposed not by monstrous youngsters but by the irreconcilable nature of adult demands. Children must be precocious and naïve, innocent and knowing. They must supply the proof of our humanity.

No wonder that children fail to meet such expectations. Any hope on Mr Cameron's part that the moral framework of the nation can be underpinned by a revival of the Aertex vest illustrates the divergence of fantasy and reality. The problem is not so much that children are being hustled into the grown-up universe. It is that adults, holding tight to infant fairy tales, still believe in Neverland.